Electric cables or other insulated electric conductors



April 17, 1956 G. D. CLOTHIER ELECTRIC CABLES OR OTHER INSULATED ELECTRIC CQNDUCTORS 3 Sheets-Sheet 1 Filed Aug. 2, 1950 By Mai Owwd ELECTRIC CABLES OR OTHER INSULATED ELECTRIC CONDUCTORS Filed Au z, 1950 April 17, 1956 vG. D. CLOTHIER 3 Sheets-Sheet 2 Inventor v 6952/52/96 M? and Attorneys April 17, 1956 G. D. CLOTHIER ELECTRIC CABLES OR OTHER INSULATED ELECTRIC CONDUCTORS Filed Aug. 2, 1950 3 Sheets-Sheet 3 I nvenior 2&45/466 A ttornev.Q

' liavingone or'mo're' apertures throughwhichithe care rod ELECTRIC GABLES ORDTHERTINSULATED ELECTRICCONDUCTORS mer e D'oriald (Zlothieg newtastieomym, aagiana Application August 2', 1950; Slerial No. 171,200

: (items nterim appiie'stiott crest Britain August 5, 19'49 6 Glaims; ct. 226+-24) This; invention r'e'late'slto electric cables or other insulatd conductors, for. heating purposes, or for power conduction purposes, such as forlighting or control or lqwvpltagepower circuits, of the kind comprising a metal sheath separated from a conducting core or cores b'y pulv ver'ulent insulating material, such for example as msgnesia, and tea process and apparatus for manufacturing such cables or conductors. t t I In the processaccording to the invention the insulating material is fed in pewdertotm to the iii't'e'rior of the sheath tube} and relativelongit'udinal movement between the sheath tube and a ram' within it is tfecte'd wherehy the ram is caused to apply a compressive thrust to the insulating owderin the sheath tube, th sa'id thrust being opposed by a frictional abutment which will yield when the'thr'ust exceeds a predetermined value" and will thereby permit the sheath tube. and theira'm' to move together unde'rzthe thrust. l

Preferably; the (frictional abutment is t adjustable for varyingi the value of thrust at which the abutment will y a p i The'relative movement between therani and the sheath tube is preferably efl ec't'e'dby positively reciprocating the ram or the sheatlituhe; In suchv case; the ra'te'at'which the" powder is fed to the sheath 'tube maybes'o c'onttolled as, to give a predetermined amount" of slip" at each compressive thrust; r

Conveniently, the rain is made hollow tubular, and; the? iiis'ula'ting powder is fedtd the sheath tube through the interiorof' the ram'; Thustherammayconsist of a hollowor tubmtr rod furnished with an" operative head or rods extend. The powder preferably e's; the-ram through=lateral ports tdan aniiiilarfe'ed opening (or' if) a" set of separate teed openings) arotir'i'd the "end ofthe' ram-m r'eadiiiesstobe compaetediiito the domain of powder in the sheath tube by the compressive thrust exer ed by the ram;

United States PatentO Suspended from a bracket A oil thegitllei-y 'jk;and

roiin't'iing' the operative lower en d of the rani'head with theshe'atli tubefC, Thelo'wer end of the ram headj isj closed by aplatehavingapertures through which the core 2,742,214 Patented Apr. 17, 1956 ice tithe D; which is in alignment with e well B an is irkewise; of a length to immerse sheath tube C within it a fixed eye. B2, carriedon a pillar B upstanding from the g ima, being provided to ensure that the shroud tube remains in alignment with the well B. t The same bracket A also serves to carry upwardly projecting bars A for supporting a driving machine, which may consist for inofi electric motoror (as shown) of a doublea ctin 'g pneumatic cylinder E fed at its ends through two fifekible pipes E conne:ct"e d through a valve indicated 5 E3 to a m 1 12 pipe F ttedfrom a source of compressed air (not shown) The valvel-E isdriven through reduction gearing E i -from a small electric lllOlQOlTE? mounted on the galleryA, the arrangement beingsuch that the two pipes E E are connected alternatively to p the main supply pipe E -throiugh the valve, the pipe E or E not connected at a particular moment to the pipe B? being opened by the valve E13 to exhaust into'the a'tmos; phere'. The piston E? (see Figure 3) in the cylinder E is carried a rod E fined to a crossbar A on the two vertical supporting barsA g so that the cylinder E is caused to reciprocate up and down in accordance with the supply ofcompressed air through the'pipe s E and E the cyliri; de'r being guided by pins E running in vertical slots A in the supporting bars A p Connected to the base oi the cylinder E is a tubular rarh F, whicheiitends downwardly within the sheath tube C around thecore rods C this ram by its reciprocation serving to tarnpthe insulating powder in the sheath tube in; manner to be described in detail later. The powder which may consist for example of magnesia, is fed to the sheathtube C through the interior of the ram F, which i'siprovided at itstupper end with a feed opening F for this purpose. j p p 7 p The powder feed mechanism may take various forms, but inthe example illustrated it is itself carried by the rani' and consists of a hopper- G, into whichthe powder can beif'e d, by hand; or otherwise, and a reciprocating plun er G below' the. hopper for pushing the powder through the feedope'ning F in the ram F. a The plunger prevent any-ingress of dust from the powder into the 7 lt 'will"b'e"appreciated that other forms of powder feed meclianisin may'be'us'e'd p l t 4.

At its lower end (see Figure 4) the tubular ram is p rdvided witl fa jdetachable head H having ports H in its wall, through which the' powder can escape fro'xjflhe interior df theram into afeed opening C annularly apertures.

I {Ia V rial, which may be'similar to that commonly used for friction brake linings, is fitted in segments within the split end of the shroud tube D to fit closely around the sheath tube C. The pressure exerted by this liner D on the surface of the sheath tube C is controlled bymeans of'a ring I surrounding the shroud tube D and having internal studs J engaging with the surface of the shroud tube. One of such studs J is adjustably mounted in the ring J and can be screwed in or out by means of a handwheel 1 so as to clamp more tightly or to loosen the grip of the liner D on the sheath tube C.

In operation, when it is desired to insert a new length of sheath tube for filling, this tube, afterthorough cleaning of its inner and outer surfaces, is let down into the well Buntil its upper end is below the lower end of the shroud tube D and the ram F. The sheath tube C is then slipped over the end of the ram within the liner D and raised (the friction grip at this stage having been loosened) until the lower end of the sheath tube is only a short distance below the lower end of the ram; The core rods C after thorough cleaning, are then pushed up through the guide apertures in the disc H their lower ends being firmly secured to an anchoring plug C which is fitted over the lower end of the sheath tube C and clamped thereto at This plug C thus seals the lower end of the sheath tube C, and it will usually be convenient to provide a packing wad C of asbestos or other suitable material against the inside of the plug C around the core rods C The friction grip handwheel I is now operated to tighten the grip and clamp the sheath tube firmly, and the pneumatic device is set into operation to reciprocate the ram F, insulating powder having been poured into the hopper G. At first the ram reciprocates idly, while a small quantity of powder is being fed into the sheath tube C. During each upward stroke of the ram, the plunger G pushes a charge of powder into the interior of the ram, and the powder falls down the ram under gravity (assisted, if desired, by vibration or agitation suitably applied to the parts) and passes through the ports H and through the feed opening C into the bottom of the sheath tube. The powder thus gradually builds up on the packing wad C in the bottom of the sheath tube until it comes in contact with the ram face at the bottom of the downward stroke thereof. The friction grip is then gradually slackened off to give the desired resistance value, while the ram compresses the small quantity of powder already in the sheath tube.

Thereafter, the downward strokes of the ram P will compress the powder firmly into the sheath tube C around the core rods C and a further charge of powder will be introduced to the ram during each upward stroke thereof. During the compression stroke, the compressive thrust of the ram on the powder will increase as the powder becomes tightly packed, until it finally exceeds the resistance of the friction grip, which will then allow the sheath tube and core rods to slip and move with the ram to the end of the compression stroke, the sheath tube thus being driven downwards by a step-by-step movement into the well B.

By suitably dimensioning the powder feed mechanism, the rate of powder supply can be so controlled that the sheath and the core rods are displaced downwardly through approximately the same distance during each downward stroke of the ram, the amount of slip being determined by the amount of powder compressed. In this way, a uniformly compacted column of powder is gradually built up in the sheath tube around the core rods. It will be clear that the drag exerted by the core rods and the sheath tube on the powder during the upstroke of the ram will assist the flow of the powder out of the apertures H and down from the annular space C into the bottom of the sheath tube, and care should be taken to shape the ram head H to provide a relatively i smooth powder flow passage and to avoid ledges against which the powder can build up;

When the sheath tube has been filled nearly to the top with powder and has therefore been moved down into the well nearly to its lowest position, the driving mechanism is stopped, and the friction grip is loosened to allow the sheath tube to be pulled down clear of the lower end of the ram. The upper end of the sheath tube'is then at once sealed, and the filled workpiece thus formed is withdrawn from the well B in readiness for its further treatment. This further treatment consists of one or .more stages of mechanical drawing, with such intermediate annealing as may be necessary, until the sheath tube, core rods and insulation have been sufficiently elongated and reduced in cross-section to produce the final sheathed cable. The mechanical drawing, of course, also assists in the consolidation and compactingof the insulating powder and, following the initial compacting by the ram, ensures a very high and'uniform density to the powder filling throughout the finished cable.

It will be understood that the foregoing arrangement has been described by way of example only and may be modified in various ways within the scope of the invention.

What I claim as my invention and desire to secure by Letters Patent is:

1. Apparatus for manufacturing electric cables or other insulated conductors of the kind in which a metal sheath is insulated from a conducting core or cores .within it by pulverulent insulating material, comprising a suspension device from which the sheath tube is freely suspended whereby the sheath tube is held stationary unless and until a thrust is exerted on it greater than a critical value, such suspension device incorporating frictional gripping means for providing the critical pressure at which the sheath tube will slip through the suspension device,

means for feeding the insulating material in powder form.

to the interior 'of the sheath tube, a ram within the sheath tube, and means for positively reciprocating the ram, whereby during each compression stroke the ram will compact the powder in the sheath tube up to that degree at which the thrust transmitted from the ram through the powder to the sheath tube is equal to the said critical value whereupon the gripping device will yield to permit the ram and the sheath tube to move as a unit for the remaining portion of the compression stroke.

2. Apparatus as claimed in claim 1, having means for adjusting the frictional gripping device whereby the critical value of thrust at which the device will yield can be varied.

3. Apparatus as claimed in' claim 1, having means whereby the feeding means for the insulating material is operated in s'ynchronism with the reciprocations of the ram.

4. Apparatus for manufacturing electric cables'or other insulated conductors of :the kind in which a metal sheath is insulated from a conducting core or cores within it by pulverulent insulating material, comprising a suspension device from which .the sheath tube is freely suspended whereby the sheath tube is held stationary unless and until a thrust is exerted on it greater than a critical value, such suspension device incorporating frictional gripping means for'providing. the critical pressure at which the sheath tube will slip through. the suspensiondevice, a hollow ramwithin thesheath tube, means for sheath tube is equal to the said critical value whereuponthe gripping device will yield to permit the ram and the sheath tube to move as a unit for the remaining portion of the compression stroke.

6. Apparatus as claimed in claim 5, in which the ram is provided with lateral ports, through which the powder escapes from the interior of the ram tube to at least one feed opening around the ram head in readiness to be compacted into the column of powder in the sheath tube by the compressive thrust exerted by the ram head thereon. v

References Cited in the file of this patent UNITED STATES PATENTS Johnson June 12, Marsh Mar. 18, Lightfoot et al July 28, Helfrecht Feb. 14, Latferty Oct. 25, Harris Mar. 24, Munger et a1 July 13,

FOREIGN PATENTS Great Britain Nov. 6, 

